Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2000-06-20
2002-11-05
Gibson, Roy D. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S102000
Reexamination Certificate
active
06477426
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a system for administering focused energy to a body selectively using either a single energy applicator or multiple microwave applicators in order to treat visable tumors and microscopic malignant and benign cells in prostate tissue with hyperthermia. The system according to the invention may be used to treat healthy tissue containing undetected microscopic pathologically altered cells (neoplasia) that are of high-water content to prevent the occurrence of or the recurrence of cancerous, pre-cancerous or benign prostatic lesions. In addition, the disclosed system and method for using the system can prevent the growth of tumors inside the prostate, as well as prevent the spread of cancer cells outside the prostate.
2. Description of the Prior Art
In order to treat prostate tumors with hyperthermia, it is necessary to heat a significant portion of the prostate gland while sparing healthy tissues in the prostate as well as the surrounding tissues including the urethral and rectal walls of a patient. In the United States there are approximately 200,000 cases of detected prostate cancer annually as well as 375,000 cases of benign prostatic hyperplasia, known as BPH, (enlarged prostate gland). BPH is a non-cancerous enlargement (tumor) of the prostate gland that occurs in almost all men as they age, particularly past the age of 50 years. In the case of BPH, the enlargement of the prostate involves the excessive growth of tissue that eventually obstructs the bladder outlet, creating difficulties with urination. In the case of prostate cancer, eventually the cancer will break through the prostate gland capsule leading to the spread of cancer to the bones and vital organs of the body. Although some of the signs of BPH and prostate cancer are the same, having BPH does not increase the chances of getting prostate cancer. Nevertheless, a patient who has BPH may have undetected prostate cancer at the same time or may develop prostate cancer in the future.
As is known in the art, the use of heat to treat prostate tumors can be effective in a number of ways; however, in most cases, the heat treatment must be capable of heating a significant volume of the prostate gland without overheating the urethral and rectal walls. In radiation therapy, the entire prostate and adjacent tissues are irradiated with x-rays to kill all the microscopic cancer cells. While heating large volumes of the prostate can destroy many or all of the microscopic carcinoma cells in the prostate, known methods of heating tumors can destroy healthy tissue in the prostate and, more damaging, in the urethral and rectal walls of a patient.
The prostate gland has electrical properties similar to muscle (T. S. England and N. A. Sharples, Nature, Vol. 163, Mar. 26, 1949, pp. 487-488.) and is known to have a high-water content, on the order of 80% (F. A. Duck, Physical Properties of Tissue, A Comprehensive Reference Book, Academic Press, New York, p. 321, 1990). Tumor tissue, in general, tends to be 10 to 20% higher in water content than normal tissue (Foster and Schepps, Journal of Microwave Power, vol. 16, number 2, pp. 107-119, 1991). Thus, prostate tumors may have a water content on the order of about 90%. Accordingly, selective microwave heating of the prostate would be the best method of targeting cancerous or benign cells.
It is well known that microwave energy can heat high-water content tumor tissues faster when compared to the heating that occurs in lower-water content normal tissues. Tumor tissue tends to be poorly perfused so blood flow often decreases at therapeutic temperatures allowing rapid heating, while in normal tissues the blood flow often increases protecting the normal healthy tissue from heat damage. Many clinical studies have established that hyperthermia (elevated temperature) induced by electromagnetic energy absorption in the microwave band, significantly enhances the effect of radiation therapy in the treatment of malignant tumors in the human body (Valdagni, et al., International Journal of Radiation Oncology Biology Physics, Vol. 28, pp. 163-169, 1993; Overgaard et al., International Journal of Hyperthermia, Vol. 12, No. 1, pp. 3-20, 1996; Vernon et al., International Journal of Radiation Oncology Biology Physics, Vol. 35, pp. 731-744, 1996). Radio-resistant cells such as S-phase cells can be killed directly by elevated temperature (Hall, Radiobiology for the Radiologist, 4
th
Edition, JB Lippincott Company, Philadelphia, pp. 262-263, 1994; Perez and Brady, Principles and Practice of Radiation Oncology, Second Edition, JB Lippincott Company, Philadelphia, pp. 396-397, 1994). Hyperthermia treatments with microwave radiating devices are usually administered in several treatment sessions, in which the malignant tumor is heated to about 43° C. for about 60 minutes. It is known that the amount of time to kill tumor cells decreases by a factor of two for each degree increase in temperature above about 43° C. (Sapareto, et al., International Journal of Radiation Oncology Biology Physics, Vol. 10, pp. 787-800, 1984). Thus, a 60-minute heat-alone treatment at 43° C. can be reduced to only about 15 minutes at 45° C., which is often referred to as an equivalent dose (t
43° C.
equivalent minutes).
During treatments with noninvasive microwave applicators, it has proven difficult to heat semi-deep tumors adequately while preventing surrounding superficial healthy tissues from incurring pain or damage due to undesired hot spots. The specific absorption rate (SAR) in tissue is a common parameter used to characterize the heating of tissue. The SAR is proportional to the rise in temperature over a given time interval times the specific heat of the tissue, and for microwave energy the SAR is also proportional to the electric field squared times the tissue electrical conductivity. The units of absolute SAR are watts per kilogram.
The first published report describing a non-adaptive phased array for deep tissue hyperthermia was a theoretical study (von Hippel, et al., Massachusetts Institute of Technology, Laboratory for Insulation Research, Technical Report 13, AD-769 843, pp. 16-19, 1973). U.S. Pat. No. 3,895,639 to Rodler describes two-channel and four-channel non-adaptive phased array hyperthermia circuits. Likewise, a non-adaptive phased array hyperthermia system was disclosed in U.S. Pat. No. 4,589,423 to Turner.
Bassen et al., Radio Science, Vol. 12, No. 6(5), November-December 1977, pp. 15-25, shows that an electric-field probe can be used to measure the electric-field pattern in tissue, and in particular, shows several examples in which the measured electric-field has a focal peak in the central tissue. This paper also discusses a concept for real-time measurements of the electric field in living specimens. However, Bassen et al. did not develop the concept of measuring an electric field using real-time with an electric-probe to adaptively focus a phased array.
The most difficult aspect of implementing hyperthermia in deep prostatic tissues, with microwave energy, is producing sufficient heating at a predetermined depth while protecting the urethral and rectal walls and surrounding organs from burns. Noninvasive multiple applicator adaptive microwave phased arrays with invasive and noninvasive electric field probes can be used for producing an adaptively focused beam at the tumor position with adaptive nulls formed in healthy tissues as described in U.S. Pat Nos. 5,251,645, 5,441,532, 5,540,737, and 5,810,888 to Fenn, all of which are incorporated herein by reference. Ideally, a focused microwave radiation beam is concentrated at the tumor with minimal energy delivered to surrounding healthy tissue. To control the microwave power during treatment, a temperature-sensing feedback probe (Samaras et al., Proceedings of the 2
nd
International Symposium, Essen, Germany, Jun. 2-4, 1977, Urban & Schwarzenberg, Baltimore, 1978, pp. 131-133) is inserted into the tumor, however, it is often difficult to accurately place the
Fenn Alan J.
Mon John
Celsion Corporation
Gibson Roy D.
Venable
Voorhees Catherine M.
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